Additive-free hollow-structured Co₃O₄ nanoparticle Li-ion battery: The origins of irreversible capacity loss

Origins of the irreversible capacity loss were addressed through probing changes in the electronic and structural properties of hollow-structured Co ₃O₄ nanoparticles (NPs) during lithiation and delithiation using electrochemical Co₃O₄ transistor devices that function as a Co₃O₄ Li-ion battery. Additive-free Co ₃O₄ NPs were assembled into a Li-ion battery, allowing us to isolate and explore the effects of the Co and Li₂O formation/decomposition conversion reactions on the electrical and structural degradation within Co₃O₄ NP films. NP films ranging between a single monolayer and multilayered film hundreds of nanometers thick prepared with blade-coating and electrophoretic deposition methods, respectively, were embedded in the transistor devices for in situ conduction measurements as a function of battery cycles. During battery operation, the electronic and structural properties of Co₃O₄ NP films in the bulk, Co₃O₄/electrolyte, and Co₃O ₄/current collector interfaces were spatially mapped to address the origin of the initial irreversible capacity loss from the first lithiation process. Further, change in carrier injection/extraction between the current collector and the Co₃O₄ NPs was explored using a modified electrochemical transistor device with multiple voltage probes along the electrical channel.